Adiponectin regulation in cardiovascular disease: is diseased fat showing its true color?

Abstract

Adipose tissue can release a plethora of factors termed adipokines. The large family of adipokines includes chemokines, cytokines, lipid factors, and growth factors. Adiponectin, the first cloned protein hormone from adipose tissue, is a metabolically active and anti-inflammatory adipokine. Adiponectin mainly circulates in different oligomeric isoforms, including high molecular weight adiponectin, that exerts different biological effects.1 Expression of adiponectin is suppressed by proinflammatory factors, reactive oxygen species, and hypoxia, whereas peroxisome proliferator activated receptor γ agonists stimulate the production of adiponectin in adipocytes. Adiponectin can improve insulin sensitivity, dampen inflammatory responses in macrophages, and induce the polarization of M2 macrophages.2 Adiponectin is negatively associated with obesity and insulin resistance, both well-established comorbidities in cardiovascular disease (CVD).3 The role of adiponectin in CVD itself is debatable because high levels of adiponectin have been associated with decreased CVD risk in asymptomatic individuals, whereas it can also predict poor prognosis in patients with established CVD.4 See accompanying article on page 2151 in the September 2014 issue From an historical perspective, adipose tissue was regarded as mere energy storage facilities. However, it is now appreciated that adipose tissue is an active tissue type, with important metabolic and endocrine functions. Classically, 2 types of adipose tissue have been identified, white and brown adipose tissue. White adipose tissue is mainly responsible for the release of adipokines, whereas the main function of brown adipose …